1. Field of the Invention
This invention relates to a method for deriving inspiration periods, expiration periods and flow rates from raw breathing flow rate data by using a half duration breath method for determining breath flow rates, and to detect flow limitation, snoring, apnea and hypopnea while eliminating noise and breathing aberrations from the flow data such that a controller on machines for treating sleep disorders can appropriately optimize the air pressure applied.
2. Description of the Related Art
In some devices pressure measurements have been used to detect abnormal breathing. In other devices methods of detecting breathing patterns use a combination of pressure and flow rates. Still other devices use airflow measurements alone where the variance in the airflow detects an apnea at an indexed value of the mid point of a normalized inspiratory flow.
Some flow rate systems for determining if a patient is inhaling or exhaling calculate an average flow rate. When the flow rate exceeds the average the patient is inhaling, when the flow rate is below average the patient is exhaling.
Another method for detecting inspiration or expiration is by use of high and low thresholds compared to a first derivative of the gas flow curve of gas delivered to the patient.
None of the methods used to date accurately detect the beginning of inspiration, the beginning of expiration or the duration and flow rates of a breath. The detection devices used to date also fail to accurately analyze or monitor breaths for snoring, apneas, hypopneas, or pauses and shifts in breathing patterns. Further the current breathing measurement devices do not accurately remove noise from the measurements.
The present breathing detectors do not measure and balance the inspiration and expiation flows.
A more accurate breath measuring method is required to provide data for sleep breathing disorder studies, to control sleep aid breathing machines and to monitor patients.